Subject: CHARMm and MPICH

From: Greg Lakatos <[email-masked]>
Date: Sun, 17 Dec 2000 01:37:14 -0800 (PST)

Hello Everyone.

Recently I've been trying to compile a parallelized CHARMm c27b2
executable with MPICH 1.2.0 on a two-machine RedHat 7 cluster and have
run into some difficulty.  In particular when compiling charmm the
command:

     ./install.com gnu large mpich

runs to completion, produces an executable, but never asks for the path
to the mpich libraries.  Moreover when charmm is run with the command:

charmm -p4wd . -p4pg hosts < inputfile.inp > outfile.out

where hosts contains:

head 0 /ptemp/charmm
head 1 /ptemp/charmm 
n01  1 /ptemp/charmm
n01  1 /ptemp/charmm

charmm issues an error over the p4wd and p4pg switches.  When run without
these switches, charmm runs but only uses a single CPU.  Any help
resolving these issues would be greatly appreciated.

- Greg

---

From: Ben Webb <[email-masked]>
Date: Sun, 17 Dec 2000 14:15:19 +0000 (GMT)

On Sun, 17 Dec 2000, Greg Lakatos wrote:

> to the mpich libraries.

	This is because you need to tell install.com to compile an MPI
binary with the "M" switch. The MPICH switch simply tells install.com
which variety of MPI you're using.

./install.com gnu large m mpich

should do the trick. (BTW, if you want to use QUANTUM, you'll need c27b3,
as there are some bugs in the c27b2 implementation on GNU platforms.)

> Moreover when charmm is run with the command:
> 
> charmm issues an error over the p4wd and p4pg switches.

	CHARMM's command line argument handling is a bit suspect, so even
a binary linked properly to the MPICH libraries will give warnings for
some MPICH options (see source/machdep/startup.src for details) but these
can be safely ignored. CHARMM compiled _with_ the M switch should at least
only treat them as warnings, not errors, though! (Oh, and another thing
about using MPICH - I would recommend explicitly specifying the number of
processors with -np, or, better still, running your binary via. mpirun.)

	Ben
-- 
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